2008 Sierra - Alarm Activation For No Know Reason

[anthony2558]

I have had my 2008 Sierra for 2 days and my alarm has activated 6 times for no know reason. Its just parked, and it decides to go off. Any thoughts? On the DIC panel it said hood open..... It was latched and secured. I jiggled the hood release lever and it stayed on. So I scrolled through the DIC displys and then it went away..... hmm.

[silverad03]

Since it's brand new, I would let the dealer handle it. Sounds to me like the alarm sensor for the hood is out of adjustment.

[anthony2558]

Yeah its going in on Monday. Its funny though. I was at the dealership explaining it to the service tech and all of a sudden the truck does its thing. Went out side, silenced the alarm and when we opened the door the cluster stated hood open. I hope its a quick fix.

[jrrod2004]

Yeah its going in on Monday. Its funny though. I was at the dealership explaining it to the service tech and all of a sudden the truck does its thing. Went out side, silenced the alarm and when we opened the door the cluster stated hood open. I hope its a quick fix.

 

It sounds like it is a sensor grounding issue (easiest) or a BCM reflash/replacement (Hardest). GM has a bulletin on it.

[anthony2558]

Yeah its going in on Monday. Its funny though. I was at the dealership explaining it to the service tech and all of a sudden the truck does its thing. Went out side, silenced the alarm and when we opened the door the cluster stated hood open. I hope its a quick fix.

 

It sounds like it is a sensor grounding issue (easiest) or a BCM reflash/replacement (Hardest). GM has a bulletin on it.

 

 

 

Really.... You know were I can get a copy of that to bring it in. Thanks.

[jrrod2004]

Here is the copy of the TSB from GM DealerWorld:

 

 

 

(Dont Try to use the links, they dont work if you dont have a USER ID and/or PASSWORD

 

 

 

Document ID# 1912477

2008 GMC Truck Sierra - 2WD

 

 

 

 

Hood Ajar Indicator/Message Malfunction

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

 

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

 

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

 

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

 

 

 

Circuit/System Description

The body control module (BCM) monitors the voltage input of the hood open switch signal circuit and the hood open closed switch signal circuit. With the hood open, the hood ajar portion of the switch is closed, grounding the hood ajar switch signal circuit from the BCM, and the hood closed portion of the switch is open. With the hood closed, the hood closed portion of the switch is closed, grounding the hood closed switch signal circuit from the BCM, and the hood ajar portion of the switch is open. During proper operation, the two separate voltage signals at the BCM should never be at the same voltage.

 

Reference Information

Schematic Reference

Remote Function Schematics

 

Connector End View Reference

Component Connector End Views

 

Description and Operation

Keyless Entry System Description and Operation

 

Electrical Information Reference

 

• Circuit Testing

 

• Connector Repairs

 

• Testing for Intermittent Conditions and Poor Connections

 

• Wiring Repairs

 

 

Scan Tool Reference

Control Module References for scan tool information

 

Circuit/System Verification

Ignition ON, observe the scan tool BCM Hood Open Switch and Hood Closed Switch parameters. With the hood open, the Hood Open Switch parameter should read Active and the Hood Closed Switch parameter should read Inactive. With the hood closed, the Hood Open Switch parameter should read Inactive and the Hood Closed Switch parameter should read Active.

 

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the hood ajar switch.

Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal C and ground.

? If greater than the specified range, test the ground circuit for an open/high resistance.

 

Ignition ON, test for 11.5-12.0 volts between the signal circuit terminal A and ground.

? If greater than the spcified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.

 

? If less than the spcified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

 

Ignition ON, test for 11.5-12.0 volts between the signal circuit terminal B and ground.

? If greater than the spcified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.

 

? If less than the spcified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

 

If all circuits test normal, test or replace the hood ajar switch.

Component Testing

Hood Ajar Switch

Ignition OFF, disconnect the harness connector at the hood ajar switch.

With the switch in the hood closed position, test for infinite resistance between the ground terminal C and the signal terminal A.

? If not infinite, replace the hood ajar switch.

 

Test for less than 2 ohms of resistance between the ground terminal C and the signal terminal B.

? If greater than the specified range, replace the hood ajar switch.

 

With the switch in the hood open position, test for infinite resistance between the ground terminal C and the signal terminal B.

? If not infinite, replace the hood ajar switch.

 

Test for less than 2 ohms of resistance between the ground terminal C and the signal terminal A.

? If greater than the specified range, replace the hood ajar switch.

 

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

 

• Hood Primary and Secondary Latch Replacement

 

• Control Module References for BCM or instrument cluster replacement, programming and setup